Everyone knows that a Leap Year occurs every 4 years when an extra day is added in February to correct the natural “drifting apart” of the calendar and the Earth’s seasons. Without it we would eventually have winter in July – not a pleasant thought. But did you know that NOT every calendar year divisible by 4 is a Leap Year?
That’s because if we continued to add an extra day every 4 years, over the course of 4 centuries, eventually we would end up with an extra 3 days. Again, winter in July… just not as quickly. So to correct that, any centennial year that is not divisible by 400 does not have an extra day added to it. So 2000 was a Leap Year, but 2100 is not. It’s divisible by 4… but not by 400. Not that I expect to be around to notice it, but I think it’s kinda neat. Effectively we leap over leap year!